Movement and habitat associations of sonic-tagged juvenile Razorback Sucker, Xyrauchen texanus, in Lake Mead, Nevada, U.S.A.

Authors: Ronald Rogers, Zachary Shattuck, Brandon Albrecht

Year: 2014 (xlvi)

Abstract

Through 18 years of study (1996-2014), the Lake Mead population of Razorback Sucker, Xyrauchen texanus, has been documented to exhibit natural recruitment. More recently (2007-2014), 72 sexually immature (juvenile) Razorback Suckers, less than 450 mm total length, have been collected in efforts associated with adult Razorback Sucker monitoring throughout Lake Mead. With a unique opportunity to study young individuals, efforts specifically targeting juvenile Razorback Sucker in Lake Mead (Las Vegas Bay, Echo Bay, the Virgin River/Muddy River inflow area) were aimed at better understanding the factors related to their recruitment. Movement and habitat association data were collected for sonic-tagged juvenile Razorback Suckers on a monthly basis during May 2013-April 2014; with additional seasonal fish community composition data collected weekly, May 2013-July 2013. These efforts helped to define seasonal habitat associations of sonic-tagged individuals through the quantification of physicochemical attributes (temperature, dissolved oxygen concentration, conductivity, pH, turbidity, and depth), and the qualitative assessment of inundated cover and substrate (type and percent composition). In the collection of the associated fish community, a number of different gears (trammel nets, hoop nets, minnow traps, and seines) were used to sample for other conspecifics. Following this approach, a total of 13 species were captured, including unmarked, wild, Razorback Suckers in direct relationship with sonic-tagged juvenile individuals. These efforts were employed for a second season with monthly habitat sampling efforts (May 2014-April 2015), and weekly fish community sampling efforts (September-November 2014). Continued research focusing on this life stage will add insight to the naturally recruiting population and potential bottlenecks of juvenile Razorback Sucker in Lake Mead, with conservation applications for the species throughout the Colorado River basin.

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